Arachidonic acid metabolites in middle ear effusions of children

Middle ear effusions (MEEs) from 78 children (98 ears) with otitis media were examined for products of arachidonic acid (AA) metabolism, including leukotrienes B4, C4, D4, and E4 and prostaglandins D2 and E2, by high-performance liquid chromatography. Leukotrienes B4 and D4 were recovered most frequently: 59% and 54%, respectively. Leukotriene B4 was found in highest concentration, 1.29 +/- 3.46 ng/0.1 mL. The concentrations of leukotrienes B4 (p less than .03), (4 (p less than .01), and E4 (p less than .02) were significantly higher in culture-positive than in culture-negative MEEs. Neither the concentration nor the type of AA metabolite correlated with bacterial species isolated, chronicity of effusion, age of subject, or consistency of MEE. These data suggest that the AA metabolites are synthesized relatively frequently during otitis media of childhood. Leukotriene B4 is the most frequently detected AA metabolite in MEEs and is highly associated with the presence of viable bacteria.

Elevated urinary leukotriene E4 excretion in patients with ARDS and severe burns

Increased synthesis of peptidoleukotrienes may occur in a variety of inflammatory diseases. To test this theory, hospitalized patients with a variety of diseases were studied and urine LTE4 quantitated as an index of total body peptidoleukotriene synthesis. 10 patients with ARDS, 7 of which had additional organ involvement, and 5 patients suffering from severe burn injuries were studied. Patients with uncomplicated ARDS excreted approximately 6-fold higher amounts of LTE4 in urine compared to healthy subjects. When ARDS was complicated by multiple organ failure (MOF), urine LTE4 levels were 2- to 150-fold higher than in healthy volunteers. Patients with severe burn injuries had peak urine LTE4 levels which were approximately 20-fold higher than in healthy volunteers. As additional controls, patients with cardiac arrhythmias (absence of inflammatory disease) and patients with uncomplicated pneumonia (localized inflammation) showed normal or mildly elevated urinary LTE4 levels. The urinary LTE4 levels in ARDS patients did not correlate with serum creatinine, bilirubin, or LDH levels, or with the WBC, nor did renal or liver failure by itself predict extremely elevated urinary LTE4 levels. In conclusion, patients with ARDS or ARDS/MOF and patients with severe injuries and sepsis syndrome excrete higher levels of urinary LTE4 than patients healthy volunteers or patients with limited inflammatory disease. In certain situations, urinary LTE4 levels may be useful as a marker of the degree of inflammation.

Capillary isotachophoretic determination of cysteinyl leukotrienes

The cysteinyl leukotrienes (LTs) C4, D4 and E4 are among the most potent lipid mediators of anaphylaxis and inflammation. A capillary isotachophoretic method is described for the determination of these cysteinyl LTs. The method is based on anionic separation and detection using UV (254 nm) and conductivity detectors. The total analysis time is of the order of 30 min. The limit of detection of the method was determined to be 0.5 nmol of LTE4. Despite of similar chemical structures, all three cysteinyl LTs can be determined simultaneously.

Urinary leukotriene E4 in patients with asthma. Effect of airways reactivity and sodium cromoglycate

A group of 17 patients with allergic asthma was challenged with aerosolized antigen, and the excretion of the peptidoleukotriene metabolite leukotriene (LT) E4 in the urine was determined as an index of leukotriene synthesis. The allergen challenge caused a drop in FEV1 of 25 to 59% within the first 2 h in all patients. This was associated with an increase in urine LTE4 excretion during the subsequent 12 h. The amount of urinary LTE4 excreted increased from a 12-h baseline level of 46 +/- 6.8 ng to a postallergen challenge level of 92 +/- 13 ng. In a similar experimental protocol methacholine challenge alone did not significantly increase urinary LTE4 excretion. In comparing all individuals as a group, there was no significant positive correlation between the magnitude of the drop in FEV1 during the immediate asthmatic response (IAR) and the increased amount of LTE4 excreted in the urine (p = 0.08). These parameters were still not significantly correlated when airways reactivity (log PC20) was also considered (p = 0.057). However, when each individual was compared to self in the presence and absence of cromoglycate, a significant correlation was found to exist between the drop in FEV1 during the IAR, the excretion of urinary LTE4, and the airways reactivity. No correlation was found between the increase in urine LTE4 excreted during the 12 h following allergen challenge and the severity of late (3 to 12 h) responses to allergen, but there was a significant prolonged (12 to 36 h) elevated urine LTE4 excretion in those patients with the most severe late asthmatic response.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of sulfidopeptide leukotriene responses in sheep tracheal smooth muscle in vitro

We have investigated the effects of leukotrienes (LTs) on isolated tracheal smooth muscle from sheep sensitive to Ascaris suum antigen. LTC4 and LTD4 produced dose-dependent contractions of sheep trachea, but LTE4 was virtually inactive. YM-17690, a non-analogous LT agonist, produced no contractile response up to 100 microM. Indomethacin (5 microM) had no effect on LTC4- and LTD4-induced contractions. L-Serine borate (45 mM), an inhibitor of gamma-glutamyl transpeptidase, shifted the dose-response curve of LTC4 to the left by 161-fold, and L-cysteine (6 mM), an inhibitor of aminopeptidase, shifted the dose-response curves of LTC4 and LTD4 to the left by 67- and 23-fold, respectively. YM-16638 (1 microM), an LT antagonist, shifted the dose-response curves of LTC4 and LTD4 to the right with pKB values of 6.57 and 7.13, respectively. YM-16638 did not affect LTC4-induced contractions of L-serine borate-treated tissues, indicating that the compound acts only on LTD4 receptors in sheep trachea, LTE4 (1 microM) shifted the dose-response curves of LTC4 and LTD4 to the right with pKB values of 6.87 and 7.31, respectively. YM-17690 (10 microM) showed effects similar to LTE4, suggesting that the compound acts as an LTE4 agonist in sheep trachea. These results suggest that in sheep tracheal smooth muscle (a) LTC4 and LTD4 produce contractions, (b) these LT-induced contractions are not mediated by cyclooxygenase products, (c) LTC4 is converted to LTD4 and then to LTE4, and (d) the potency of the LTC4- and LTD4-induced contractions is increased when their conversion to LTE4 is inhibited.(ABSTRACT TRUNCATED AT 250 WORDS)

Action of peptidoleukotrienes on ion transport in rabbit distal colon in vitro

Serosal but not mucosal addition of the peptidoleukotrienes, leukotriene (LT) C4 (LTC4), LTD4 and LTE4 transiently (maximal response within 2 min) increased short-circuit current (Isc) and transepithelial conductance across stripped rabbit colonic mucosa mounted in Ussing chambers. All three peptidoleukotrienes elicited their responses in the presence of amiloride (10 microM) and were inhibited by serosal addition of the NaCl cotransport inhibitors bumetanide (100 microM) and furosemide (1 mM). The effects of the peptidoleukotrienes on Isc and transepithelial conductance were concentration-dependent with maximal effects occurring at 10 microM. Half-maximal effects were produced at 30 nM for LTC4, 50 nM for LTD4 and 450 nM for LTE4. The secretory responses to both LTD4 and LTE4 were antagonized in a concentration-dependent manner by the LTD4/LTE4 receptor antagonist, SK&F 104353 (2(S)-hydroxy-3-(R)-[(2-carboxyethyl)thio]-3-[2-(8 phenyloctyl)phenyl]propanoic acid). Complete inhibition of the LTD4 and LTE4 effects were observed at 0.1 microM SK&F 104353 and half-maximal effects were achieved at 0.6 nM SK&F 104353. At 10 microM SK&F 104353 only 50% inhibition of the LTC4-induced increase in Isc was observed. These results suggest the peptidoleukotrienes stimulate colonic Cl- secretion by receptor-mediated mechanisms and that receptors for LTC4 are distinct from those mediating the action of LTD4/LTE4.

Metabolism and cardiovascular effects of leukotrienes in warm- and cold-acclimated American bullfrogs (Rana catesbeiana)

Sulfidopeptide leukotrienes are important mediators in mammals, but much less is known of their metabolism and action in nonmammalian vertebrates. This study examines the cardiovascular effects of leukotrienes on blood pressure and heart rate and compares the metabolism of leukotrienes in vivo and in vitro in warm- and cold-acclimated bullfrogs. Leukotriene C4 (LTC4) is more potent than leukotriene D4 (LTD4) and leukotriene E4 (LTE4) in eliciting hypotension. The leukotrienes are more potent in warm-acclimated animals. Conversion of [3H]LTC4 to [3H]LTD4 occurs rapidly in warm-acclimated bullfrogs, with 15.2 +/- 1.7% of the [3H]LTC4 remaining at 1.5 min. Conversion is slower in vivo in cold-acclimated frogs, with 20.2 +/- 1.7% of the [3H]LTC4 remaining by 6 min. In blood taken from warm-acclimated frogs, conversion of [3H]LTC4 to [3H]LTD4 occurs more rapidly at 22 than at 5 degrees C. This pattern is similar in blood taken from cold-acclimated frogs, suggesting that no modification of gamma-glutamyl transpeptidase occurs at low temperature. [3H]LTE4 production is not observed in vivo or in vitro during the time course of the experiments. The rapid metabolism of LTC4 to LTD4 may represent an inactivation mechanism in amphibians. The cardiovascular effects of LTC4 in vivo may be much greater than current measurements indicate because of rapid conversion of LTC4 to the less potent LTD4.

Delayed treatment with an LTD4/E4 antagonist limits pulmonary edema in endotoxic pigs

We used a selective leukotriene (LT) D4/E4 receptor antagonist (LY 203647) to investigate the role of cysteinyl LTs as mediators of several important pathophysiological events in a porcine model of endotoxic shock. Pentobarbital-anesthetized pigs (11.8-17.5 kg) were mechanically ventilated with 100% O2. Pigs in groups I (n = 10), IIA (n = 10), and IIB (n = 5) were infused with Escherichia coli lipopolysaccharide (LPS; 250 micrograms/kg) from time (t) = 0-20 min. Pigs in group III (n = 3) were normal controls. All pigs were resuscitated from t = 0-240 min with Ringer lactate (0.8 ml.kg-1.min-1). Pigs in group I received no further treatment. At t = 30 min, groups IIA and IIB were injected with LY 203647 (30 mg/kg) and were started on an infusion of the compound at 10 (group IIA) or 30 mg.kg-1.h-1 (group IIB). Delayed treatment with LY 203647 significantly (P less than 0.05) and persistently ameliorated LPS-induced pulmonary hypertension. The compound also abrogated LPS-induced pulmonary edema, as assessed by gravimetrically determined lung extravascular wet-to-dry weight ratios. Despite its beneficial effect on pulmonary edema, delayed treatment with LY 203647 did not improve arterial oxygenation. Delayed treatment with LY 203647 transiently improved mesenteric perfusion. These data suggest that cysteinyl LTs are important mediators in porcine endotoxicosis.

Enhanced urinary excretion of leukotriene E4 by patients with multiple trauma with or without adult respiratory distress syndrome

1. The aim of the present study was to evaluate the systemic synthesis of cysteinyl leukotrienes in patients with multiple trauma. In order to do this, the urinary excretion of leukotriene E4 was assessed in the first 10 days after trauma. 2. Leukotriene E4 was unequivocally identified by g.c.-m.s. in the urine of healthy subjects and patients with multiple trauma after its conversion to 5-hydroxyeicosanoic acid. Leukotriene E4 was routinely isolated from 24 h urine samples by solid-phase extraction followed by reverse-phase h.p.l.c. and was subsequently quantified by r.i.a. 3. Healthy subjects excreted daily 10 +/- 3 nmol of leukotriene E4/mol of creatinine (mean +/- SEM, n = 16) into urine. 4. Patients with multiple trauma who did not develop adult respiratory distress syndrome (n = 7) excreted 76.8 +/- 6.7 nmol of leukotriene E4/mol of creatinine (mean +/- SEM) daily during the first 10 days after trauma, which was significantly (P less than 0.01) more than did healthy subjects. 5. Excretion of leukotriene E4 was even more enhanced in three patients with multiple trauma who developed adult respiratory distress syndrome. Maximal amounts of 593 +/- 185 nmol of leukotriene E4/mol of creatinine (mean +/- SEM) were excreted on day 9 after trauma by these three patients, which corresponds to a 7.7- and a 59-fold increase in excretion of leukotriene E4 compared with patients with multiple trauma who did not develop adult respiratory distress syndrome and healthy subjects, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise-induced urinary excretion of leukotriene E4 in children with atopic asthma

Urinary levels of leukotriene (LT) E4, a stable end-product of LTC4 and LTD4, were measured before and after exercise in 10 children with severe asthma and seven children with moderate asthma using HPLC and RIA to clarify the relationship of LT to the severity of asthma and to the degree of bronchospasm in exercise-induced asthma. The urinary LTE4 level significantly increased after exercise in the severe asthma group, but not in the moderate asthma group (14.3 +/- 14.5 to 24.3 +/- 20.6 versus 19.6 +/- 12.3 to 17.6 +/- 10.8 ng/mmol creatinine, p less than 0.05). The urinary LTE4 level increased in 10 patients (eight with severe asthma), and it decreased in seven patients (five with moderate asthma). A significant difference in the degree of bronchospasm after exercise (as shown by the maximal % fall in the peak expiratory flow rate), was seen when patients with increased urinary LTE4 excretion were compared with those with decreased excretion (60.4 +/- 17.3 versus 24.1 +/- 14.3%, p less than 0.01). Our findings suggest that exercise-induced asthma, or at least a subtype of exercise-induced asthma, may partly develop through the release of LTC4.

Cysteinyl leukotriene actions on the microcirculation of the normal and split hydronephrotic rat kidney

The effects of leukotriene D4 (LTD4) and leukotriene E4 (LTE4) on renal microcirculation were determined on normal and hydronephrotic female Wistar rats. In normal kidneys, the effects of LTD4 on total renal blood flow and glomerular filtration rate were measured by a flow meter and by inulin clearance. In the split hydronephrotic kidney, the LTD4- and LTE4-mediated vascular effects were localized by intravital microscopy. Intravenous infusion of low-dose LTD4 (1 x 10(-9) mol min-1 kg-1) over 15 min induced a strong decrease in renal blood flow (-43% and -70%) in the normal and the hydronephrotic kidney. After the infusion the glomerular filtration rate of the normal kidney was significantly reduced by 65% and the filtration fraction by 32%. The fall in filtration fraction is in accordance with the significant decrease in luminal diameters of the arcuate artery (-28%) and the proximal interlobular artery (-12%) in the hydronephrotic kidney under LTD4. The decrease in renal blood flow, glomerular filtration rate, filtration fraction and luminal diameters persisted in the normal as well as in the hydronephrotic kidney for more than 60 min beyond cessation of infusion. Local application of LTD4 (1 x 10(-10) mol l-1 up to 1 x 10(-7) mol l-1) and LTE4 (1 x 10(-10) mol l-1 up to 1 x 10(-8) mol l-1) induced a dose-dependent constriction of the arcuate artery and the proximal interlobular artery. The distal interlobular artery, the afferent and the efferent arteriole were not significantly affected by LTD4 or LTE4. The glomerular blood flow was dose-dependently reduced up to 48% under local LTD4 and 43% under LTE4. The LTD4/LTE4 antagonist FPL 55712 (1 x 10(-8) mol min-1 kg-1, iv) significantly attenuated the effects of LTD4 infusion and local LTE4 application in the hydronephrotic kidney. This is indicative of the presence of receptors for LTD4 and LTE4 in the larger preglomerular vessels of the rat kidney. The LTD4 effects on the normal kidney were attenuated by simultaneous infusion of dopamine (5 microgram min-1 kg-1) or plasma expansion, two principal methods in the treatment of acute renal failure. The results in the normal and hydronephrotic kidney demonstrate a preferential preglomerular vasoconstriction under LTD4 and LTE4 causing a marked decrease in renal and glomerular blood flow, glomerular filtration rate and filtration fraction.

Effect of the leukotriene LTD4/LTE4 antagonist, SR 2640, in ulcerative colitis: an open clinical study

This investigation was performed in order to examine the role of sulfidopeptide-leukotrienes in a chronic inflammatory bowel disease, ulcerative colitis, by use of the recently developed LTD4/LTE4 antagonist, SR 2640 (2-[3-(2-quinolylmethoxy)phenylamino]benzoic acid). Eight ulcerative colitis patients with a mild to moderate disease activity were included in this open and uncontrolled study and SR 2640, 250 mg t.i.d., was administered for 6 weeks. Treatment of the patients with SR 2640 reduced the inhibitory effect of LTD4 on LTB4-directed chemotaxis of neutrophils purified from their blood. This indicates that the dose administered was sufficiently high to obtain systemic LTD4 receptor antagonism. Three of the 8 patients were in clinical remission at the end of the study, and the lack of clinical symptoms persisted for at least 2 months after discontinuing the drug. The condition of 3 patients was unchanged, and that of 2 patients deteriorated after 5 weeks, requiring treatment with sulphasalazine and steroids. SR 2640 was well tolerated by all patients. In a previously published study dealing with 4 weeks sulphasalazine treatment in the same category of patients, remission rates of 5% and 25% were found in the placebo and sulphasalazine groups, respectively, and the remission rate of SR 2640 thus seems to be of the same magnitude as that of sulphasalazine. The serum and faecal concentrations of SR 2640, and its metabolite, the beta-glucuronide, were found to be lower in ulcerative colitis patients as compared to healthy volunteers, and it is therefore possible that altered pharmacokinetics of SR 2640 is present in patients with chronic inflammatory bowel disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a 5-lipoxygenase inhibitor on leukotriene generation and airway responses after allergen challenge in asthmatic patients

The effect of a single oral dose (800 mg) of zileuton (A-64077), a specific 5-lipoxygenase inhibitor, on the early and late airway responses to inhaled allergen was studied in a randomised, double blind, placebo controlled, and crossover trial in nine subjects with atopic asthma. Leukotriene generation was also assessed in vivo by measuring urinary leukotriene (LT) E4 excretion, and ex vivo by measuring calcium ionophore stimulated whole blood LTB4 production. Zileuton almost completely inhibited ex vivo LTB4 production but reduced urinary excretion of LTE4 by only about half. There was a trend for the early asthmatic response to be less on the day of zileuton treatment, but this did not reach statistical significance (p = 0.08). The zileuton induced reduction in maximum fall in FEV1 in the early asthmatic response was, however, significantly related to the reduction in urinary LTE4 excretion (r = 0.8), but not to the reduction in LTB4 generation ex vivo. There was no significant change in the allergen induced late asthmatic response, or in the increase in airway responsiveness to methacholine following antigen. The results provide some support for the hypothesis that the cysteinyl leukotrienes have a role in the allergen induced early asthmatic response. More complete in vivo inhibition of 5-lipoxygenase may be needed to produce a significant reduction in airway response to allergen challenge.

A monoclonal antibody against the sulfidopeptide leukotrienes LTC4, LTD4 and LTE4

A monoclonal antibody (1A-LDR1) against sulfidopeptide leukotrienes (LT) is described. The mAb shows a nearly identical detection limit of about 0.04 ng for LTC4, LTD4, LTE4 and NacLTE4 in standard fluid phase RIA. Steric modifications, however, diminish the sensitivity, as determined for the examples 5-epi-LTC4, 6-epi-LTC4, 5,6-epi-LTC4 and 11-trans-LTC4. No crossreactivity could be observed for LTB4. Crossreactions with components of the LT peptide chain such as L-cysteine or glutathione, as well as with arachidonic acid, were not detectable. In assessing the accuracy of the LT-RIA, recovery experiments with supernatants of mouse peritoneal macrophages and incubates of gastric mucosa showed a good correlation of r = 0.993 and 0.990, respectively. Results of an inhibition experiment with mouse peritoneal macrophages, incubated with several concentrations of indomethacin and nordihydroguaiaretic acid (NDGA), support the reliability of RIA and ELISA. The new LT-mAB allows an almost complete detection of peptide leukotrienes in one assay.

Leukotriene C4 disposition and metabolism in the anesthetized and endotoxemic dog

The metabolism and disposition of tritiated leukotriene C4, [3H]-LTC4, were studied in control dogs and endotoxin-treated dogs. Radioactivity was monitored in plasma, bile, and urine for 4.5 hr after an IV bolus of [3H]-LTC4. A decreased recovery of radioactivity in bile and urine was observed in the endotoxin-treated dogs. Cumulative [3H]-LTC4 metabolic patterns in bile and urine were determined by reverse-phase high-performance liquid chromatography (RP-HPLC) separation. Three primary metabolites, [3H]-LTD4, [3H]-LTE4, and a polar metabolite, (0.15-0.19)LT, accounted for most of the total bile radioactivity. The same primary metabolites were found for endotoxin-treated dogs and in similar relative amounts. [3H]-LTE4 and the polar metabolite (0.15-0.21)LT were the primary metabolites found in urine, but no N-acetyl LTE4 was found in bile or urine for either group. Plasma incubation of [3H]-LTC4 revealed heat-sensitive dipeptidase and glutamyl transpeptidase activity with significant production of [3H]-LTD4 and [3H]-LTE4 after 5- and 30-min incubation. Pharmacokinetic analysis using the two-compartment open model revealed an increased distribution phase rate constant (alpha) and distribution phase half-life [t1/2(alpha)], and decreased clearance (ClB), volume of distribution [Vd(ss) and Vd(area)] and elimination rate microconstant (Kel) of tritiated leukotrienes for endotoxin-treated dogs. This analysis along with the maintained higher plasma levels of tritiated leukotrienes, [3H]-LTs, in endotoxin-treated dogs suggests that endotoxin caused a decreased body clearance and less peripheral tissue penetration of [3H]-LTs. Collectively, these results indicate that the metabolism of LTC4 to LTD4 and LTE4, but not N-acetyl LTE4, in dogs was similar to that reported for man, pig, and monkey but dissimilar to rat. Endotoxin did not affect the types or relative amounts of metabolites found in bile or urine but appears to affect the disposition of [3H]-LTs by decreasing clearance and distribution.

On the relation between cerebral cysteinyl-leukotriene formation and epileptic seizures

In gerbils pentylenetetrazole- or handling-induced seizures were accompanied by cerebral formation of small amounts of cysteinyl-leukotrienes (LT) but large amounts of prostaglandin (PG) F2 alpha. By contrast, in rats injected with pentylenetetrazole or bicuculline very large amounts of PGF2 alpha but no cysteinyl-LT could be detected in the brain tissues. The data indicate that at least in rats the extensive neuronal activity during tonic-clonic convulsions is not necessarily sufficient for the activation of the 5-lipoxygenase pathway. Apparently important species differences do exist.

Inhibition of leukotriene biosynthesis and polymorphonuclear leukocyte functions by orally active quinolylmethoxyphenylamines

The N-substituted quinolylmethoxyphenylamines, ETH603, ETH615 and ETH647, inhibited the formation of LTB4 in rat peritoneal leukocytes, human peripheral polymorphonuclear leukocytes and canine whole blood. In rat and human cells, the compounds also inhibited the formation of 5-HETE and stimulated the synthesis of 15-HETE. In rat leukocytes, the compounds were 15-30 times more potent inhibitors of LTB4 synthesis than nordihydroguaiaretic acid, but in canine whole blood they were significantly less potent, possibly due to protein binding. However, after oral administration of the compounds to dogs a long-lasting inhibition of LTB4 production in peripheral blood was observed at serum concentrations much lower than those required in vitro. Furthermore, the compounds inhibited the LTB4-directed chemotaxis and the phagocytosis of C. albicans blastospores by canine polymorphonuclear leukocytes both in vitro and following oral administration. The calcium ionophore A23187-induced release of LTB4 in the peritoneal cavity of rats was also inhibited by systemic administration of the compounds. We therefore conclude that these novel quinolines are orally active 5-lipoxygenase inhibitors which may accumulate in inflammatory cells in vivo, leading to potent inhibition of leukotriene biosynthesis and cell function.

Nasal inflammatory mediator release in ragweed allergic rhinitis: correlation with cellular influx into nasal secretions

Lipid-derived mediators are found in nasal secretions during the early and late phase of allergic responses. To explore this early response further, concentrations of inflammatory mediators were measured along with characterization of specific cell influx during dose-dependent ragweed challenges. Ten allergic rhinitis subjects underwent two unilateral nasal lavages using 3-fold concentrations of short ragweed antigen. Low doses of ragweed (0.016-0.114 units Amb a I) did not provoke cell influx (1 of 18 challenges), whereas moderate doses (0.432-1.3 units Amb a I) induced cell influxes in 7 of 18 and at high doses in 8 of 17 challenges (3.39-11.7 units Amb a I). The differential of the cellular influx was greater than 50% neutrophils in 7 challenges; greater than 50% eosinophils in 3, and a mixed pattern in 6. There was a significant association between the dose of antigen and the level of prostaglandin D2 (PGD2), leukotrienes (LTs) C4, D4 and E4. Challenges with an eosinophilic influx tended to be associated with higher concentrations of mediators than neutrophilic influxes. Similar to the immediate skin response, the early allergic response in the nose demonstrated a cell influx with release of PGD2, LTsC4, D4 and E4. Nasal cellular inflammation therefore can occur within minutes of allergen exposure.

Leukotriene E4 elimination and metabolism in normal human subjects

Radiolabeled leukotriene (LT) E4 was infused into three healthy subjects in order to assess the production and elimination of sulfidopeptide leukotriene metabolites in urine. Three different radiolabeled tracers were employed, [14,15-3H]LTE4, [35S]LTE4, and [14C] LTE4 in five separate infusion studies. There was a rapid disappearance of radioactivity from the vascular compartment in an apparent two-phase process. The first elimination phase had an apparent half-life of approximately 7 min. Radioactivity quickly appeared in the urine with 10-16% eliminated during the first 2 h following intravenous infusion; 7%, 2-5 h; 4%, 5-8 h; 4%, 8-15 h; and 1.5%, 15-24 h from the [14C] LTE4 experiments. Unmetabolized LTE4 was the major radioactive component in the first urine collection, but at later times two more polar compounds predominated. After extensive purification by normal phase-solid phase extraction and reverse-phase high performance liquid chromatography, these compounds were characterized by UV spectroscopy, co-elution with synthetic standards, negative ion electron capture gas chromatography/mass spectrometry, and tandem mass spectrometry. The two major urinary metabolites were structurally determined to be 14-carboxy-hexanor-LTE3 and the conjugated tetraene, 16-carboxy-delta 13-tetranor-LTE4. Three other minor metabolites were detectable in the first urine collection only and were characterized by co-elution with synthetic standards as 16-carboxy-tetranor-LTE3, 18-carboxy-dinor-LTE4, and 20-carboxy-LTE4. omega-Oxidation and subsequent beta-oxidation from the methyl terminus appeared to be the major metabolic fate for sulfidopeptide leukotrienes in man. The accumulation of the 14-COOH-LTE3 and 16-COOH-delta 13-LTE4 may reflect a rate-limiting step in further oxidation of these compounds which places a conjugated triene or conjugated tetraene, respectively, two carbons removed from the CoA ester moiety. Also in the first urine collection there was another minor metabolite identified as N-acetyl-LTE4, however, no subsequent beta-oxidation of this metabolite was observed. The major metabolites of LTE4 might be useful in assessing in vivo production of sulfidopeptide leukotrienes in humans.

Leukotriene D4 and E4 induce transmembrane signaling in human epithelial cells. Single cell analysis reveals diverse pathways at the G-protein level for the influx and the intracellular mobilization of Ca2+

Leukotrienes are recognized as important mediators of the inflammatory process. Recently, increasing attention has been paid to the role of noninflammatory cells in the regulation of the inflammatory process. To further increase our knowledge of this matter we have, in the present study, investigated leukotriene-induced Ca2+ signaling, using a single cell technique in a human epithelial cell line, Intestine 407. It was evident that both LTD4 and LTE4, at physiological concentrations (10 nM), triggered rapid and pronounced cytosolic free Ca2+ transients, due to both influx across the plasma membrane and intracellular mobilization. Preincubation with pertussis toxin (1200 ng/ml) decreased the level of agonist-induced Ca2+ transients to an extent similar to that caused by depletion of extracellular Ca2+, suggesting that the toxin affected the influx but not the intracellular mobilization of Ca2+. Indeed, by using the Mn2+ quenching technique, it could be shown that pertussis toxin totally inhibited the influx of Ca2+. The fact that, even after pertussis toxin treatment, direct G-protein activation by AIF4- was still able to trigger a cytosolic free Ca2+ transient, indicates that, in these cells, G-proteins (GTP-binding proteins) that are insensitive to pertussis toxin are capable of mediating a Ca2+ signal. In order to test the idea that such G-proteins regulate mobilization of intracellular Ca2+ induced by LTD4 and LTE4, we electropermeabilized and preincubated the Intestine 407 cells with guanosine-5'-O-(2-thiodiphosphate) (GDP beta S), let them reseal, and, after loading with fura2, investigated the effects on agonist-stimulated Ca2+ signaling. Electropermeabiization and resealing alone did not significantly affect the Ca2+ responses triggered by LTD4 or LTE4. Addition of GDP beta S, in the presence of extracellular Ca2+, reduced the Ca2+ responses by approximately 60-70%. In Ca2(+)-depleted medium, GDP beta S also impaired the LTD4-induced response by 65%, however, it had no effect on the Ca2+ response induced by LTE4. In conclusion, LTD4 and LTE4 trigger cytosolic free Ca2+ signaling in a human epithelial cell line by causing both an influx of Ca2+ and mobilization of intracellular Ca2+. The Ca2(+)-signaling mechanism appears to consist of dual pathways, since the influx is regulated by a pertussis toxin-sensitive G-protein, but, the mobilization of Ca2+ is not. Furthermore, our data suggest that the LTD4-induced mobilization is regulated by a pertussis toxin-insensitive G-protein whereas the LTE4-induced mobilization is relatively insensitive to both pertussis toxin and GDP beta S.

Leukotrienes in the sputum and urine of cystic fibrosis children

1. Leukotrienes (LTs) are potent pro-inflammatory mediators with actions relevant to the pathophysiology of cystic fibrosis (CF), including increased mucus production, bronchoconstriction, leucocyte chemotaxis, and increased vascular permeability. We have therefore investigated the potential role of LTs in children with CF. Leukotriene E4 levels were assessed in the urine of 30 normal (N) children (aged 1.3-12.7 years) and 30 CF children (1.6-14.3 years). Sputum from 13 of the CF children was analysed from LTB4, LTC4, LTD4, and LTE4. LTs were separated by reversed-phase h.p.l.c. and quantitated by radioimmunoassay. 2. Urinary LTE4 levels were log normally distributed, with geometric mean values (95% confidence intervals) of N: 88.4 (71.3-111) pmol mmol-1 creatinine (n = 30), and CF: 112 (70.6-177) pmol mmol-1 creatinine (n = 30; P greater than 0.05). Of the CF subjects, 33% had urinary LTE4 levels above 200 pmol mmol-1 creatinine, compared with 3.3% of the N children. 3. In sputum, mean (+/- s.e. mean) LT concentrations were (pmol g-1), LTB4: 44.3 +/- 10.8, LTC4: 4.9 +/- 1.3, LTD4: 1.8 +/- 0.9, and LTE4: 67.7 +/- 18.9 (n = 13). 4. Urinary LTE4 levels correlated significantly with sputum LTE4 levels (r = 0.673, P = 0.012), and with sputum levels of total cysteinyl-LTs (r = 0.660, P = 0.014). 5. In conclusion, total cysteinyl-LT content in sputum is 10-fold higher than previously reported, consisting primarily (91%) of LTE4. The high levels of LTE4 and LTB4 in sputum suggest involvement of LTs in the pathophysiology of CF. Urinary LTE4 levels may prove useful as a marker for cysteinyl-LT production in sputum.